Figure 5.1: Electrical transmission towers like the one shown in this picture help deliver the
electricity that you use for energy every day. ( 4 )
The main reason is that almost everything that happens on Earth involves energy. Most of
the time when something happens, energy is changing forms.
Eventhoughenergydoeschangeform, thetotalamountofenergyalwaysstaysthesame. The
Law of Conservation of Energy says that energy cannot be created or destroyed. Scientists
discovered this law by noticing that any time they observed energy changing from one form
to another, they could measure that the overall amount of energy did not change.
For an example of how energy changes from one form to another, think about what goes
on when you kick a soccer ball. Your body gets its energy from food. When your body
breaks down the food you eat, it stores the energy from the food in a form calledchemical
energy. But some of this stored energy has to be released to make your leg muscles move.
When this happens, the energy that is released changes from chemical energy to another
form, calledkinetic energy. Kinetic energy is the energy of anything in motion. Your
muscles move your leg, your foot kicks the ball, and the ball gains kinetic energy by being
kicked. So you can think of the action of kicking the ball as a story of energy moving and
changing forms. The same is true for anything that happens involving movement or change.
Potential energyis energy that is stored. Potential energy has the potential to do work
or the potential to be converted into other forms of energy. An example of potential energy
might be the ball you kicked, if it ended up at the top of a hill.